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Dunbar's Number

Cap the working set of warm, mutually-tracked social bonds an individual can hold at roughly 150, because pairwise-relationship tracking scales as O(N-squared) against a fixed neocortical budget, with nested inner shells at ~5, ~15, and ~50.

Core Idea

Dunbar's Number is the finding that the human neocortex imposes an upper limit of roughly 150 on the stable, mutually-tracking social relationships an individual can simultaneously maintain. It is not a count of contacts but of the cognitive-tracking load of named-individual bonds, which scales as O(N-squared) against a fixed budget. The 150 layer is nested — a ~5 support clique, ~15 sympathy group, ~50 active network — with outer shells near 500 and 1500.

Scope of Application

Dunbar's Number is bounded to one substrate — the human neocortex carrying one edge-type, the warm reciprocal named-individual bond — so it lives across the human social sciences that study it, while the setting changes from field to field.

  • Social and cognitive psychology — the home: working-memory-for-people, the nested shells, capacity versus motivation.
  • Evolutionary anthropology — modal hunter-gatherer band and pre-modern village size, the comparative-primate setting.
  • Organizational design — the small-cell move: split a unit before it crosses ~150.
  • Sociology of religion — the "felt-as-a-family" congregation size before small-group ministry becomes necessary.
  • Online-community design — separating follower counts from the reciprocal-interaction graph that carries the load.
  • Military organization — the company-sized unit (~150) where everyone-knows-everyone coordination still holds.

Clarity

Naming this ceiling separates the roster of contacts one is connected to from the working set of relationships actively tracked — only the warm, mutually-modeled tie carries the O(N-squared) load the budget caps. It also separates capacity from motivation and value, so a small active network is a property of working-memory-for-people rather than temperament, and "make more friends" cannot move a ceiling that is cognitive, not motivational.

Manages Complexity

A group's coordinative life looks like an unbounded mess needing bespoke cultural explanation. Dunbar's Number collapses that sprawl onto one governing quantity — where the active-bond count sits relative to the layer boundaries. Because the ceiling is a threshold, not a slope, it imposes a small branch structure: below 150 coordination runs on shared knowledge; at saturation the regime shifts to hierarchy and formal roles, the felt intimacy loss reading as capacity, not decay.

Abstract Reasoning

The number licenses a diagnostic move re-reading a regime change as a saturating tracking budget rather than cultural decay and placing a network among shells. Its interventionist move pre-engineers the split or coordinating layer before the ceiling bites. Its boundary-drawing move fixes working-set-not-roster, capacity-not-value, threshold-not-slope, and one substrate, supporting forecasts of coordination regime and intimacy depth from one layered count.

Knowledge Transfer

Within the human social sciences the finding transfers as mechanism across one neocortex substrate carrying the warm reciprocal bond — anthropology, org design, sociology of religion, online communities — the number and shells carrying without translation. Beyond that substrate the honest reading is shared abstract mechanism: the general capacity-bounded-tracking-yielding-a-ceiling-and-regime-change pattern travels, but the figure 150, the primate regression, and the neocortical edge-type do not; software- or pheromone-coordinated systems have their own ceilings carried by the parent pattern, not by this number.

Relationships to Other Abstractions

Local relationship map for Dunbar's NumberParents appear above the current abstraction, mutual partners to the right, and children below. Node labels state whether each abstraction is prime or domain-specific; colors identify relation types.Dunbar's NumberDOMAINPrime abstraction: Constraint — is a kind ofConstraintPRIME

Current abstraction Dunbar's Number Domain-specific

Parents (1) — more general patterns this builds on

  • Dunbar's Number is a kind of Constraint Prime

    Dunbar's number specializes constraint to a cognitively bounded working set of mutually tracked social relationships.

Hierarchy path (1) — routes to 1 parentless root

Neighborhood in Abstraction Space

Dunbar's Number sits in a moderately populated region (53rd percentile for distinctiveness): it has near-neighbors but no dense thicket of look-alikes.

Family — Social Perception & Self-Referential Bias (23 abstractions)

Nearest neighbors

Computed from structural-signature embeddings · 2026-07-12